William and Caroline Herschel:

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William and Caroline Herschel
Incredible Siblings of Science
Shreyans Parekh Astronomy 007 Professor Langacker
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Biographies
William Herschel

• Born November 15, 1738 in Hanover, Germany
• Successful music teacher and bandleader
• Music led him to math and astronomy
• Appointed court astronomer to King George III
• Became one of most notable observers in history
  of astronomy
• Pioneer in study of stars

Major accomplishments together 1.
Observations helped to double the known size of
universe 2. First to accurately describe
Milky Way 3. Mapping of spiral nebulae
4. Discovery of Uranus (1781) 5. Pushed
forward science of building telescopes
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Charting Stars and Milky Way Part 1

• First astronomers in history to do systematic
  survey of the night sky
• Discovered many stars that they previously
  observed as single stars were resolving, because
  of larger telescopes used, into double (or
  binary) stars
• Stars appeared to move around each other,
  suggesting gravitational influence between them
• Showed that Keplers laws of planetary motion
  and Newtons law of universal gravitation
  applied, not only to the planets and sun of our
  solar system, but to distant stars as well and
  were truly universal
• Stars were so distant that they were not able to
  determine their distances with parallax, so they
  came up with another method for determining the
  shape of the Milky Way

Source http//www.enchantedlearning.com/subjects/
astronomy/glossary/indexh.shtml
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Charting Stars and Milky Way Part 2

• Noticed that density of stars varied depending
  upon what region he was looking at
• Two factors could account for this varied
  distribution of stars
• 1. Either the stars were closer together in
  the regions where they appeared to
• be more compacted
• 2. Stars were spaced apart more or less
  uniformly, and where the stars
• seem to be the densest is where the
  Milky Way extended out the furthest
• Discovered greatest density of stars was around
  the Milky Way and lowest density was away from
  the Milky Way
• Concluded shape of Milky Way detached nebulae
  was a disk (grindstone)

Source http//www.enchantedlearning.com/subjects/
astronomy/glossary/indexh.shtml
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Cataloguing Nebulae

• Over 25 years, he catalogued and investigated
  nebulae, milky luminous patches in sky and
  verified that they were clusters of countless
  stars
• Expanded list of nebulae compiled by one of his
  contemporaries Charles Messier and believed they
  were island universes
• Announced discovery in his Catalogue of 500 New
  Nebulae and Clusters of Stars
• Identified about 2,500 planetary nebulae (hazy
  clouds that surrounds stars) and more than 800
  binary stars (pairs of stars orbiting common
  center of galaxy)
• In 1835, Lord Rosse designated nebulae that
  resembled whirlpools of light were spiral nebulae

Herschels 40-foot reflector
Source http//www.thoemmes.com/encyclopedia/hersc
hel.htm
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Discovery of Binary Stars

• Tried to find relative distances of stars and
  each other and from Sun
• Definition pair of stars bound together by
  gravity
• Discovered binary stars in 1802 and described
  them as union of two stars, that are formed
  together in one system, by the laws of
  attraction.
• Concluded from the motions of double stars that
  they are held together by gravitation and that
  they revolve around a common center, thus
  confirming the universal nature of Newton's
  theory of gravitation

Source http//www.hao.ucar.edu/Public/education/b
ios/herschel.html
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Grindstone Model of Universe

• Definition Sun is located near the center of
  the of a wheel-shaped group of stars. Milky Way
  is flat like a grindstone.
• Counted stars along 683 lines of sight
• Assumed all stars are same luminosity, and that
  they could see edges of the universe
  (underestimated size of universe)
• Accomplishment established idea of the Milky
  Way as an autonomous celestial body, and extended
  boundaries of universe much further than anyone
  had previously thought them to be
• Erroneous assumption dark regions represent
  gaps in the Milky Way (are in fact dark clouds of
  dust)

Herschels Milky Way and detached nebulae model
Source http//www.enchantedlearning.com/subjects/
astronomy/glossary/indexh.shtml
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Discovery of Uranus

• Discovered on March 13, 1781 and was first
  planet discovered in modern times
• While systematically searching for double stars,
  Herschel discovered what he thought to be a comet
  but due to its completed orbit, found it was a
  planet
• Called Georgium Sidus after King George III of
  England, but renamed to Uranus from Greek meaning
  sky
• Credited with discovering two moons of Uranus
  (Titania and Oberon) as well as two moons of
  Saturn (Enceladus and Mimas)

Image taken by Voyager 2
Source http//www.hao.ucar.edu/Public/education/b
ios/herschel.html
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Interesting Facts

• William was a prolific telescope maker
• His 40-foot reflector was largest in the world
  until the 1840s, when Lord Rosse completed
  construction of Leviation of Parsonstown
• Discovered infrared radiation by passing
  sunlight through prism and holding a thermometer
  before red end of the spectrum
• Coined term asteroid to describe star-like
  appearance of small moons
• Wild speculator believed all planets and even
  the Sun were inhabited by life forms

Source http//hometown.aol.com/deepskyguy1/willia
mherschel.html